\documentstyle{article}
\textwidth 18cm
\textheight 23cm
\oddsidemargin -1cm
\topmargin 0cm
\parskip 0.15cm
\parindent 0pt
\small
\begin{document}
\def\izq#1{\hbox to -1.5pt{\hss#1}}
\arrayrulewidth 0.04cm
\begin{tabular}{|p{8.5cm}p{8.5cm}|} \hline
& \\
\multicolumn{2}{|c|}{\LARGE\bf THE\hspace*{1cm}STAR\hspace*{1cm}FORMATION\hspace*{1cm}NEWSLETTER} \\ [0.3cm]
\multicolumn{2}{|c|}{\large\em An electronic publication dedicated to early stellar evolution and molecular clouds} \\ [0.3cm]
{\hspace*{0.8cm} No. 38 --- 18 Nov 1995 } & \multicolumn{1}{r|}{Editor: Bo Reipurth (reipurth@eso.org)\hspace*{0.8cm}} \\ [-0.1cm]
& \\ \hline
\end{tabular}
\vspace*{1cm}
\begin{center}
{\Large\em From the Editor}
\end{center}
\vspace*{0.3cm}
This issue of the Newsletter has unfortunately been significantly
delayed due to a serious malfunction in our computer system.
\vspace*{0.8cm}
\begin{center}
{\Large\em Abstracts of recently accepted papers}
\end{center}
\vspace*{0.6cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Millimeter Interferometric Polarization Imaging of the
Young Stellar Object \\ NGC~1333/IRAS~4A }}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ R.L. Akeson, J.E. Carlstrom, J.A. Phillips, and D.P. Woody }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{Owens Valley Radio Observatory, California Institute of Technology,
MS 105-24, Pasadena, CA 91125, USA}
%% Within the following brackets you place your text:
{We present a 3.4~mm polarization image of the dust emission associated
with the young stellar object NGC~1333/IRAS~4A made with the Owens
Valley Millimeter Array with 5$''$ resolution. The
integrated linear polarization of the dust continuum is 4\% of the
total intensity. The polarization is produced by magnetically aligned
dust grains and arises from very dense gas ($n > 10^8$~cm$^{-3}$)
indicating the dust alignment process remains viable in the dense
protostellar envelope. The magnetic field directions inferred from
our observations are aligned with features seen in the high velocity
outflow emanating from IRAS~4A. The magnetic field directions are not
aligned with the field on much larger scales as measured by optical
and infrared selective extinction, suggesting significant field
structure in the cloud core. The peak of the polarized emission is
offset from the total intensity peak, perhaps indicating considerable
unresolved structure in the magnetic field.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astrophys. J. Letters }
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Star Counts in Southern Dark Clouds: Corona
Australis and Lupus}}
{\bf{ C.M.Andreazza$^1$ \ and J.W.S.Vilas-Boas$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $ª..$ indicates your author number, for
$^1$ {Instituto Astronomico e Geofisico, USP, Av Miguel
Stefano 4200, 04301-904, Sao Paulo, Brazil} \\
$^2$ {CRAAE-INPE, EPUSP/PTR, CP 61548, CEP 05424-970, Sao
Paulo, Brazil}
{E-mail contact: carmen@vax.iagusp.usp.br or
jboas@spider.usp.br}
%% Within the following brackets you place your text:
{Star counts technique is used towards southern dark globular
filaments situated in the cloud complexes of Corona Australis
and Lupus. Tables and maps of the distribution of visual
extinction are presented for each filament. Lower limit masses
for the filaments and condensations have been estimated and it
is also given the central coordinates of the condensations. R
CrA is the most massive active star forming region among the
filaments studied in this work whereas Lupus 1, with almost
the same lower limit of mass, has only a few T Tauri stars and
just one young embedded object. The distribution of direction
of the magnetic field in the condensations of Lupus, suggest
that the condensation morphologies does not have any apparent
relation with the magnetic field orientation}
% Here you write which journal accepted your paper, for
{ Astron. \& Astrophy. Suppl. }
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{ The optical jet of RW Aurigae:
excitation temperature and ionization state from long-slit spectra}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ F. Bacciotti$^1$, G. A. Hirth$^2$ \ and A. Natta$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Dipartimento di Astronomia e Scienza dello Spazio, Universit\`a
di Firenze, Largo E. Fermi 5, I--50125 Firenze, Italy} \\
$^2$ {Max-Planck-Institut f\"{u}r Astronomie, K\"onigstuhl 17,
D-69117 Heidelberg, Germany } \\
$^3$ {Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5,
I--50125 Firenze, Italy }
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: fran@arcetri.astro.it}
%% Within the following brackets you place your text:
{The physical properties of the optical jet associated with the T
Tauri star RW Aurigae are discussed. The excitation temperature, the
hydrogen ionization fraction, the electron and gas densities are
estimated in various positions along the flow axis using a diagnostic
technique originally developed for the study of the physical
conditions in highly collimated Herbig-Haro jets (Bacciotti, Chiuderi
\& Oliva, 1995, A\&A 296, 185). The receding portion of the jet (red
lobe) has an ionization fraction which is slowly decreasing from about
25\% near the star to about 2\% at a distance of 6-7$''$ ($\sim$1000
AU); the hydrogen density is roughly constant with a value of about
10$^4$ cm$^{-3}$; the temperature shows a slight decline, with typical
values of about 4500 K. These results are consistent with the idea
that the gas is initially ionized in the jet acceleration zone and
that the physical conditions in the visible part of the jet are
determined by time-dependent hydrogen recombination. It has not been
possible to obtain any result for the blue lobe, due to the weakness
of the [SII] 6716,6731 \AA\ lines. The mass-loss and momentum rate in
the flow (red lobe) are $\dot{M} \sim 5~ 10^{-8} $ M$_{\odot}$
yr$^{-1}$ and $\dot{P} \sim 6.5~ 10^{-6} $ M$_{\odot}$ yr$^{-1}$ km
s$^{-1} $. }
% Here you write which journal accepted your paper, for example:
{ Accepted by A \& A }
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{The Narrow Emission Lines of T Tauri Stars}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ C.C. Batalha$^1$, N.M. Stout--Batalha$^{1,2}$, G. Basri$^3$,
\ and M.A.O. Terra$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Observat\'{o}rio Nacional, Departamento de Astrof\'{\i}sica,
R. Jose Cristino 77, Rio de Janeiro } \\
$^2$ {University of California,
Board of Studies in Astronomy and Astrophysics,
Santa Cruz, CA 95064, USA } \\
$^3$ {University of California,
Astronomy Department,
Berkeley, CA 94720, USA}
%% Within the following brackets you place your text:
{We present the first comprehensive study of the narrow emission lines of
T Tauri Stars (TTS). These narrow lines have been reported in the
literature as originating in the stellar atmosphere and having gaussian
type profiles centered at the stellar rest velocity, with a basewidth
not larger than 50 km s$^{-1}$. Here, we concentrate on the CaII lines
$\lambda$$\lambda$ 8498, 8542 and 8662 and the helium line $\lambda$
5876. After applying veiling corrections,
the average narrow component line emission
is found to be larger than that found in active main sequence stars: up
to several times larger for classical T Tauri with strong rates of disk
accretion. More striking is the finding that the resulting line
emission strengths of these lines correlate with veiling. The
correlation is confirmed on individual stars for which observations at
several epochs exist and for which veiling varies widely on relatively
short timescales. We also find a correlation between the narrow
emission fluxes and the near infrared excesses for stars with low levels
of veiling, which includes the few weak--lined TTS of the sample.
We discuss possible formation sites for the narrow emission lines in the
classical TTS, and we present simple models to explain the observations.
In these models, the excess line emission found for the stars with
higher accretion rates is assumed to originate in localized regions near
the magnetic footpoints of the accretion column. We refer to these
hypothetical regions in the atmosphere collectively as the ``hot
chromosphere" since we assume they are additionally heated by the
reprocessed energy of the colliding gas in the accretion process.
Computing two chromospheric models: one representing the typical weak
TTS chromosphere and the other representing the best guess at the ``hot
chromosphere", we find the following. The ``hot chromosphere" is
characterized by a steep temperature gradient beginning at low continuum
optical depths in order to simultaneously give the large observed
central flux and the relatively narrow baselines ( 50-60 km s$^{-1}$). The
chromosphere temperature rise is not similar to the earlier deep
chromosphere models in which a sudden chromospheric temperature rise is
appended to the photosphere at relatively large mass column. For the
most extreme cases (i.e. largest line fluxes), 20\%, at most, of the
star's surface must be covered by ``hot chromospheric" regions. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. J. }
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{RNO\,43: a jet-driven super-outflow}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{S.\,J.\,Bence, J.\,S.\,Richer \ and R.\,Padman}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
Mullard Radio Astronomy Observatory, Cavendish Laboratory, Madingley Road,
Cambridge, CB3 0HE, United Kingdom
%% Within the following brackets you place your text:
{We present $21''$-resolution, CO observations of the spectacular
molecular outflow associated with RNO~43. This outflow extends over
nearly 5~pc and is thus one of the largest known. The high velocity
CO emission is broken up into several distinct regions of high
excitation. Each of these regions subtends a small angle at the young
stellar object driving the flow, and four show coincident optical
emission in the form of Herbig-Haro objects, supporting the hypothesis
that the collimated jet responsible for the Herbig-Haro objects also
drives the molecular outflow. The jet is episodic and wanders in
direction. We show that the asymmetries in the outflow can be
explained by a symmetrical jet propagating in an asymmetrical cloud.
The jet has had a considerable heating effect on a large fraction of
the volume of its parent molecular cloud.}
% Here you write which journal accepted your paper, for example:
{ Accepted by M.N.R.A.S.}
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Density Structure in Giant Molecular Cloud Cores}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Edwin A. Bergin$^{1,2}$, Ronald L. Snell$^1$, \ and Paul F. Goldsmith$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Five College Radio Astronomy
Observatory, Department of Physics and Astronomy, University of
Massachusetts, Amherst, MA 01003, USA} \\
$^2$ {Current address: Smithsonian Astrophysical Observatory MS-66, 60 Garden Street, Cambridge, MA 02138-1596, USA
} \\
$^3$ {National Astronomy and Ionosphere
Center, Department of Astronomy, Cornell University, Ithaca, NY
14853-6801, USA
}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: ebergin@cfa.harvard.edu}
%% Within the following brackets you place your text:
{We present the results of a multitransition study of HC$_3$N in cores
of three giant molecular clouds in Orion, M17, and Cepheus A. In
these regions we have mapped the J = 4 $\rightarrow$ 3, J = 10
$\rightarrow$ 9, J = 12 $\rightarrow$ 11, and J = 16 $\rightarrow$ 15
transitions of HC$_3$N over a 4$'$ $\times$ 12$'$ area (360 positions)
in Orion and a 4$'$ $\times$ 5$'$ area (120 positions) in M17 and
Cepheus A. We have used the results of a previous study of the
temperature structure of the dense gas in the same cloud cores
together with a non-LTE excitation model for HC$_3$N to derive the
density of molecular hydrogen and the column density of HC$_3$N. In
all we have computed densities for 133 positions in Orion, 46
positions in M17, and 14 positions in Cepheus A. Despite the
differences between the clouds, the range of densities in the three
cores is found to be quite similar, with derived values of n$_{H_{2}}$
between 3 $\times$ 10$^{5}$ and $5 \times 10^6$ cm$^{-3}$.
The principal result of this study is that, in spite of the use of an
optically thin tracer and the inclusion of an improved source
temperature model, the density within each cloud core shows no
evidence of large scale variations. These observations are consistent
with the results of previous efforts which utilized other tracers of
the dense gas and assumed a constant temperature for the cloud. An
examination of the size scale of the clouds implied by the observed
density and the C$^{18}$O column density demonstrates that either each
cloud has a strikingly ($>$10:1) flattened geometry, each with the
short axis along the line of sight, or that the dense gas must be
clumped and is filling only a small fraction of the volume
($^{$ 100.
}
% Here you write which journal accepted your paper, for example:
{ To appear in Ap.J., March 20, 1996}
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{Rotation Periods of Stars in the Orion Nebula Cluster:
The Bimodal Distribution}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf {P. I. Choi \ and W. Herbst}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{Astronomy Department, Wesleyan University, Middletown, CT 06459, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: bill@elysium.astro.wesleyan.edu}
%% Within the following brackets you place your text:
{Results from the 1992-93 season of imaging fields in the Orion Nebula
Cluster at Van Vleck Observatory are presented. Data were obtained on
525 stars brighter than I $\sim$ 16 mag and 50 periodic variables were
found, of which 27 are newly discovered. Light curves of these spotted
stars are displayed. The number of rotation periods known for ONC
members, based on four years of monitoring at VVO, now stands at 75
and a comprehensive list is given here. Since candidate objects were
selected only by proper motion and position, without reference to
spectral, X-ray, infrared or other properties, the sample provides a
relatively unbiased view of the angular velocity distribution of low
mass stars at an age of around one million years. Twenty-five stars
have periods determined in more than one year and in 23 cases they
agree to better than 1\%. In one case the agreement is within 5\% and
in one case there is evidence of period doubling. Seventy stars have
amplitudes consistent with cool spots; the other five are interpreted
as hot spot stars. The frequency distribution of rotation periods is
distinctly bimodal, confirming the discovery of Attridge \& Herbst
(1992). About one-third of the stars are rapid rotators with a median
period of 2.55 days and dispersion of 0.7 days. The others are slow
rotators with a median of 8.3 days, a dispersion of 3.8 days and a
tail of very long period stars extending to 34.5 days. Six stars have
rotation periods exceeding 12 days, which had been proposed as a limit
for T Tauri stars. Our observations support theories of
disk-regulated rotational evolution during the pre-main sequence
phase. Slow rotators are interpreted as stars ``locked" to their
accretion disks and rapid rotators are presumed free of such locking.
The gap in the frequency distribution at rotation periods near 4 days
is interpreted as a portion of angular velocity space through which
contracting stars pass quickly once released from the disk lock. We
find a significant difference between the period distributions of the
more and less nebulous fields within the ONC; the more nebulous
(arguably younger) fields have a larger proportion of slow rotators.
Combining the ONC sample with one drawn from the Tau-Aur region, we
show that most pre-main sequence stars more nearly conserve angular
velocity than angular momentum as they contract, consistent with
predictions of the disk-interaction theories. A large amount of
angular momentum loss appears to occur as a result of this process
during the early stages of pre-main sequence evolution. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. J.} \ { This paper is available via the World Wide Web at
http://sun.astro.wesleyan.edu/herbst.html}
\vspace{0.3cm}
{\large\bf{The occurrence of H$_2$O
masers in the early stages of star formation}}
{\bf{C. Codella$^{1,2}$, M. Felli$^{3}$, V. Natale$^{4}$}}
$^1$ {Max Planck Institut f\"ur Radioastronomie, Auf dem H\"ugel 69,
D-53121 Bonn, Germany} \\
$^2$ {Dipartimento di Astronomia e Scienza dello Spazio,
Universit\`a di Firenze
Largo E. Fermi 5, 50125, Firenze, Italy} \\
$^3$ {Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125, Firenze, Italy} \\
$^4$ {C.N.R., C.A.I.S.M.I., Largo E. Fermi 5, 50125, Firenze, Italy}
{E-mail contact: codella@mpifr-bonn.mpg.de}
{The results of a survey of 22.2 GHz water maser emission toward 39
young stellar objects (McCutcheon et al. 1991) are presented. The
sample contains bright IRAS sources associated with molecular clumps,
which may represent different phases of the early evolution of star
forming regions, depending on the presence or absence of compact
H\,{\sc ii} regions. We associate 19 water masers with the IRAS
sources, 4 of which are new detections. Taking into account also
previous detections of masers that were quiescent during our survey,
the total number of sources which show maser emission is 22 (56\% of
the whole sample). This has to be taken as a lower limit if
variability of the maser emission is considered. The maser percentage
does not change for sources with or without a compact H\,{\sc ii}
region. It is higher (68\%) if we consider only sources associated
with large CO linewidths.
Our H$_{2}$O observations confirm that water masers can occur at the
earliest phases of the formation of high luminosity stars, much before
the development of an ionized region detectable in the radio
continuum, and that they are closely connected with molecular
outflows.}
{Accepted by Astron. Astrophys.}
\newpage
%% Between these brackets you write the title of your paper:
{\large \bf{Further characteristics of the young triple system TY~CrA}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Patrice Corporon, Anne-Marie Lagrange \ and Herv\'e Beust
}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{Laboratoire d'Astrophysique de Grenoble, BP 53X F-38041 Grenoble
C\'edex, France}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: corporon@gag.observ-gr.fr}
%% Within the following brackets you place your text:
{ The pre-main sequence star TY~CrA is an eclipsing multiple system;
in addition to the spectroscopic signatures of the primary and the
secondary, lines from a third component were recently detected. Here
we present high resolution spectra of the Li~{\sc i}~6708~\AA, [S~{\sc
ii}]~6716,6731\,\AA, and [O~{\sc i}]~6300\,\AA\ lines. Observations
were carried out with the Coud\'e Echelle Spectrograph at the 1.4\,m
ESO CAT Telescope, in remote control during the year 1994 and in La
Silla in April 1995. [S~{\sc ii}] and [O~{\sc i}] emission lines are
undoubtedly detected. They are the first narrow emission lines
observed so far in the TY~CrA visible spectrum. Their origin remains
uncertain, but they might be due to the tertiary component. Our
long-term monitoring of the Li~{\sc i} lines of the tertiary component
and previously published results allows us to derive its orbital
motion around the binary system. We computed various possible fit for
the orbit of this third component, and estimate its dynamical and
physical attributes. The five solutions present in fact remarkable
common features: 1) a semi-major axis of the order of 1\,A.U., with an
orbital period significantly less than 1 year; 2) a rather high
eccentricity (four solutions have $e\simeq 0.5$); 3) a tertiary mass
$m_3\simeq 1.2$ -- $1.4\,M_\odot$, although this parameter is weakly
constrained (large uncertainty); 4) an inclination $i\simeq 16$ --
$25^\circ$. The orbit appears thus to be eccentric and highly inclined
with respect to that of the binary. The tentative determinations of
orbital elements for the tertiary need to be tested through additional
high S/N data, in particular to reduce the number of relevant
solutions. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. \& Astrophys. }
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{High-Velocity Ammonia emission Associated with
the Young Stellar Object Serpens FIRS~1}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Salvador Curiel$^{1,2}$, Luis F. Rodr\'\i guez$^1$, Jos\'e F. G\'omez$^3$,
Jos\'e M. Torrelles$^3$, Paul T.P. Ho$^2$ \& Carlos Eiroa$^4$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Instituto de Astronom\'\i a, UNAM, Apdo. Postal 70-264,
04510 M\'exico, D.F, M\'exico} \\
$^2$ {Harvard-Smithsonian Center for Astrophysics, 60 Garden Street,
Cambridge, MA 02138, USA} \\
$^3$ { Instituto de Astrof\'\i sica de Andaluc\'\i a, CSIC,
Apdo. de Correos 3004, C/Sancho Panza S/N, E-18080 Granada, Spain} \\
$^4$ {Dpto. F\'\i sica Te\'orica, C-XI, Facultad de Ciencias,
Universidad Aut\'onoma de Madrid, Cantoblanco, 28049 Madrid, Spain}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: scuriel@astroscu.unam.mx}
\def\lax {\ifmmode{_5$ and have probable detections for another 5. V~773\,Tau,
a weak emission line binary system, is remarkable in that its 2.7 mm
continuum decreased from $\sim 30$ mJy to $\sim 0$ mJy in less than
six months. We find that the singles are, on average, stronger 2.7
continuum sources than the multiples, consistent with Osterloh \&
Beckwith's (1995) finding at 1.3 mm. Significant estimates of the
sizes have been obtained for 8 singles. They imply large ($R > 150$~AU)
disks, with relatively flat density distribution (emissivity
flatter than $r^{-1.5}$). The spectral
energy distributions in the millimeter range can be fitted
using a dust emissivity law $K_{\nu} \propto \nu^{\beta}$ with
value of $\beta$ in the range 0.5 to 1.
Only DG\,Tau, Haro 6-5b and UY\,Aur have detectable \tco~\juz emission.
\tco~ emission, but no 2.7 mm continuum, is also found in the
LkH$\alpha$ 332 region and near FS\,Tau;
however, it does not appear to be associated with the known
stars. Interpreting the observational results in terms of the
circumstellar disk scenario, we find that, in all cases, disk masses
derived from the dust emission at 2.7 mm are more than a factor of
about 20 larger than the masses derived from the \tco~\juz upper limit. }\\
{ Accepted by A\&A main journal}
{Postcript files are available by WWW on IRAM home page:
http://iram.fr/papers/papers.html or by anonymous ftp
account to iram.fr: /dist/pub/papers/e021.ps.Z}
%
%\end{document}
%
\newpage
%% Between these brackets you write the title of your paper:
\newcommand{\fdg}{\hbox{$.\!\!^\circ$}}
\newcommand{\ionhy}{H{\sc ii}}
\newcommand{\degr}{$^\circ$}
{\large\bf{A Survey of the Galactic Plane for 6.7-GHz Methanol Masers I: \\
$l$ = 325\degr -- 335\degr\/ ; $b$ = -0\fdg53 -- 0\fdg53}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{S.P. Ellingsen$^1$, M.L. von Bibra$^1$, P.M. McCulloch$^1$,
R.P. Norris$^2$, A.A. Deshpande$^{1,3}$ and C.J. Phillips$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Physics Department, University of Tasmania, GPO Box 252C, Hobart 7001,
TAS, Australia} \\
$^2$ {Australia Telescope National Facility, PO Box 79, Epping 2121,
NSW, Australia} \\
$^3$ {Raman Research Institute, Bangalore 560080, India}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: Simon.Ellingsen@phys.utas.edu.au}
\newcommand{\methanol}{$\mbox{CH}_{3}\mbox{OH}$}
\newcommand{\transa}{$5_{1}\rightarrow6_{0}\mbox{~A}^{+}$}
%% Within the following brackets you place your text:
{We report the results of the first complete survey of an area of the
Galactic Plane for maser emission from the 6.7-GHz \transa\/
transition of \methanol\/. The survey covers a 10.6-square-degree
region of the Galactic Plane in the longitude range 325\degr --
335\degr\/ and latitude range -0\fdg53 -- 0\fdg53. The survey is
sensitive to masers with a peak flux density greater than $\sim$
2.6~Jy. The weakest maser detected has a peak flux density of 2.3~Jy
and the strongest a peak flux density of 425~Jy. We detected a total
of 50 distinct masers, 26 of which are new detections. We show that
many 6.7-GHz \methanol\/ masers are not associated with {\em IRAS}
sources, and that some are associated with sources that have colours
differing from those of a typical ultra-compact \ionhy\/ region
(UC\ionhy). We estimate that the number of UC\ionhy\/ regions in the
Galaxy is significantly more than suggested by {\em IRAS}-based
estimates, possibly by more than a factor of two.}
% Here you write which journal accepted your paper, for example:
{Accepted by MNRAS, preprint available via http://reber.phys.utas.edu.au/$\sim$sellings}
\vspace{0.5cm}
%% CFG definitions
%%
\def\spose#1{\hbox to 0pt{#1\hss}}
\def\lta{\mathrel{\spose{\lower 3pt\hbox{$\mathchar"218$}}
\raise 2.0pt\hbox{$\mathchar"13C$}}}
\def\gta{\mathrel{\spose{\lower 3pt\hbox{$\mathchar"218$}}
\raise 2.0pt\hbox{$\mathchar"13E$}}}
\def\au{{\rm\,AU}}
\def\cm{{\rm\,cm}}
\def\gm{{\rm\,g}}
\def\yr{{\rm\,yr}}
\def\msun{{\rm\,M_\odot}}
%% Between these brackets you write the title of your paper:
{\large\bf{Layered Accretion in T Tauri Disks}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Charles F. Gammie}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{Center for Astrophysics, MS-51, 60 Garden St., Cambridge, MA
02138, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: cgammie@cfa.harvard.edu}
%% Within the following brackets you place your text:
{
We put forward a model for accretion disks around T Tauri stars.
The model assumes that angular momentum transport is driven
by magnetic fields, and can occur only in those parts of
the disk that are sufficiently ionized that the gas can
couple to the magnetic field. These regions lie at
$R \lta 0.1 \au$, where collisional ionization is effective,
and at $R \gta 0.1 \au$ in a layer of thickness $\approx 100
\gm \cm^{-2}$ at the surface of the disk where cosmic ray
ionization is effective.
The model predicts that the stellar accretion rate is about
$10^{-8}\msun\yr^{-1}$, independent of the rate of infall
onto the disk. Matter that is not accreted onto the star
accumulates in the inner few AU of the disk at a rate of
about $10^{-3}\msun$ in $10^4\yr$. Given this buildup it
is unlikely that accretion is steady. The effective temperature
profile is $T_e \sim r^{-1/2}$ outside of $0.1\au$, which differs
from the canonical $T_e \sim r^{-3/4}$. We calculate the
expected spectral energy distribution for the disk and show
that this temperature profile produces an infrared excess.
Finally, we discuss some of the leading uncertainties in the
theory.
}
% Here you write which journal accepted your paper, for example:
{Accepted by Ap.J.}
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Non-LTE Effects in Ammonia}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{R.A. Gaume,$^1$ T. L. Wilson,$^{2,3}$
K. J. Johnston,$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1${U.S. Naval Observatory, 3450 Massachusetts Ave. NW, Washington DC
20392-5420, USA} \\
$^2${Max Planck Institut f\"{u}r Radioastronomie, Postfach 2024,
D-53010 Bonn, Germany}\\
$^3${Astronomy Department, Univ. of Illinois, Urbana, IL 61801, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: gaume@nh3.usno.navy.mil}
%% Within the following brackets you place your text:
{The non-LTE effects in the NH$_3$ (J,K)=(1,1) absorption toward the DR21 HII
region have been investigated using a spatial resolution of 1.7$\rightarrow$3
arcseconds. The anomalies, found in the satellite hyperfine (HF) components,
indicate significant, widespread departures from LTE. We present images of the
LTE departure for the inner and outer pairs of NH$_3$ (1,1) HF components
toward the HII region, and find surprisingly, that the degree of LTE departure
for these HF components is spatially {\bf anticorrelated}. Previous models
predicted a spatial correlation. This unexpected result may be explained by a
dynamic model involving both the infall and outflow of molecular
material. Although weak emission in the redshifted outer HF component is
widespread toward the continuum, an unresolved, high brightness temperature
($\ge$600K) maser is found just SW of the continuum peak. This is the first
proven instance of an interstellar maser in the NH$_3$ (1,1) level. The flux
density of the maser is larger than the absolute value of the flux density of
any of the other HF components (seen in absorption), including the main
component.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Ap.J. {\it Letters}}
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Dynamics of embedded protostar clusters in clouds }}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Uma Gorti \ and H.~C.~Bhatt }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{Indian Institute of Astrophysics, Bangalore 560034, India} \
{E-mail contact: gorti@iiap.ernet.in}
%% Within the following brackets you place your text:
{This is the abstract of your paper}
The dynamics of clumps and protostars in a young protocluster
system embedded in its parent molecular cloud are studied here
through numerical simulations. It is found that the presence of
massive clumps and their dynamics strongly affects the motion
of the lower mass protostars. Mass segregation of clumps due to
dynamical drag by the interclump gas results in the formation of
a dense central region and the lower mass protostars get
preferentially ejected out of the cloud via gravitational
encounters. The protostellar cluster is found to gradually
expand with time forming a more extended system than the clumps.
Thus, embedded protostar clusters are probably dynamically evolved
systems with large halos of low mass protostars. This explains
observations of T Tauri stars, which appear to be isolated from
active star-forming sites and are in regions devoid of dense
gas. As multiple star formation sites in clouds are common, outer
members are subject to velocity perturbations due to massive
clumps and other clusters, possibly leading to a faster removal
of objects.
%% Here you write which journal accepted your paper, for example:
{ Accepted by M.N.R.A.S }
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{The Unusually Rich Infrared Emission-Line Spectrum of a
Deeply Embedded Low Luminosity YSO}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Thomas P. Greene$^1$ and Charles J. Lada$^2$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Institute for Astronomy, University of Hawai`i, 2680 Woodlawn
Drive, Honolulu, HI 96822 USA} \\
$^2$ {Harvard-Smithsonian Center for Astrophysics, 60 Garden Street,
Cambridge, MA 02138 USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: greene@ifa.hawaii.edu}
%% Within the following brackets you place your text:
{We have discovered a rich, near-infrared, emission-line spectrum from
IRAS 04239+2436, a low-luminosity ($L \sim 1.3 L_{\odot}$) deeply embedded
(Class I) source in the Taurus dark clouds. This Class I Young
Stellar Object shows emission lines of Na I, H$_2$, H I Pa$\beta$, and
nearly the entire H I Br series as well as prominent emission in the
vibrational overtone bands of CO. This is the lowest luminosity YSO
yet observed which exhibits CO overtone bands in emission and is the
only source in a survey of approximately 100 low-luminosity YSOs which
shows both strong CO and nearly the entire Br series of H I in
emission. Unlike most other sources known to show this emission, the
central star of this YSO is probably neither hot nor luminous enough
to produce the observed CO emission via surface heating of an
optically thick circumstellar disk. It is possible that the CO
emission originates in a powerful stellar wind, but this cannot be
confirmed with presently available data. The H$_2$, Na I, and H I
emission lines are suggestive of a stellar wind, and we find that the
H I Br $\gamma$ line luminosity is consistent with published wind model
calculations. The observed H I Pa$\beta$ to Br$\gamma$ line ratio falls
within the range observed for T Tauri stars and within the range of
wind model predictions, but we cannot be certain whether these as well
as the other atomic lines form in a wind or in some other component of
circumstellar gas. Higher spectral resolution observations are
required to determine the exact origins of the CO and atomic emission
features of this fascinating object.}
% Here you write which journal accepted your paper, for example:
{ Accepted by The Astrophysical Journal for the April 10, 1996 issue}
\vspace{0.5cm}
{\large
\bf
The $\beta$ Pictoris phenomenon among young stars. III.\\
The Herbig Ae stars WW Vul, RR Tau and BF Ori}
{\bf V.P. Grinin$^{1}$, O.V. Kozlova$^{1}$, P.S. Th\'e$^{2}$, and
A.N. Rostopchina$^{1}$}\\
e-mail:grinin@crao.crimea.ua\\
$^1$ Crimean Astrophysical Observatory, Crimea, 334413, Nauchny, Ukraine\\
$^2$ Astronomical Institute ``Anton Pannekoek", University of Amsterdam, Kruislaan 403,\\
1098 SJ Amsterdam, Netherlands
The Herbig Ae stars RR Tau, BF Ori and WW Vul are members of the small
subclass of young stars with Algol-type brightness variability.
There are reasons to assume that they are surrounded by young
protoplanetary disk-like envelopes, oriented edge-on and that they are
young progenitors of the star $\beta$ Pictoris. In this paper we present
spectroscopic evidences for this assumption.
They are based on the observations of variable redshifted absorption
components in the sodium Na\,{\sc i} $D$ resonance lines, similar to those
found in the spectrum of UX Ori. The shortest time scale of their
observed variability is one day (BF Ori, WW Vul).
Their maximum radial velocities reach 200-300 km s$^{-1}$, which corresponds
to a distance from the star of a few stellar radii.
As in the case of UX Ori we connect the formation
of such absorption components with the evaporation of star-grazing bodies in
the vicinity of young hot stars.
The fact that high-velocity redshifted absorption components are
systematically observed in the sodium Na\,{\sc i} $D$ lines in the spectra
of several UX Ori type stars, excludes the interpretation of this phenomenon
by a special orientation of star-grazing orbits relative to the observer.
We connect such an asymmetry with the evaporation of small (meteor-like)
bodies which dissipate completely before the periastron of their orbits
are reached, in their movements towards the stars.\\
Accepted by Astronomy and Astrophysics
\vspace{0.5cm}
{\large\bf Orientation of the circumstellar disks of the Herbig Ae/Be
stars and statistics of the H$_{\alpha}$ line profiles}
%\vspace{1.0cm}
{\bf V.P.Grinin and A.N.Rostopchina}
%
%\vspace{0.5cm}
Crimean Astrophysical Observatory, Crimea, 334413, Nauchny, Ukraine\\
e-mail: grinin@crao.crimea.ua\\
%\vspace{0.5cm}
The results of statistical analysis of
the published data on the photopolarimetric activity of
Herbig Ae/Be stars and the H$_{\alpha}$ line profiles in
their spectra are presented. They confirm the
availability of connection between the type of the H$_{\alpha}$ profile and
the level of photopolarimetric activity of young stars: the single
profiles and the $P$ Cygni ones are observed predominantly at
the photometrically quiet stars whereas two-component profiles
(typical for the disk accretion) more often in stars with a high
level of the photometric activity. Existence of such a connection means
that the variety of the observed H$_{\alpha}$ line profiles can be
explained in the framework of one model of axially-symmetrical gas
envelope observed under the different inclination to the line-of-sight.
The mechanism of formation of such envelopes is discussed.
Accepted by Russian Astronomical Journal
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Infrared lines for measuring the magnetic field strength
of T~Tauri stars}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Eike~W.~Guenther \& James P. Emerson}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{Department of Physics, Queen Mary \& Westfield College,
Mile End Road, London E1 4NS, United Kingdom}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for
%% example:
{E-mail contact: E.Guenther@qmw.ac.uk}
%% Within the following brackets you place your text:
{Although magnetic fields are highly important for understanding the
structure and evolution of T~Tauri stars (TTS), very few attempts
measure these fields have actually been reported, because of the high
dispersion, and long integration times that are usually needed in the
optical regime. In this paper we point out that the
$1.5630$-$1.5695\mu$m regime in the near infrared contains a number of
suitable lines for this purpose, and present spectra which confirm the
presence and strengths of these lines in the weak line T Tauri stars Tap
35 (=NTTS 042417+1744) and V410 Tau. We demonstrate that, using these
lines and modern IR grating spectrometers such as the UKIRT's CGS4, the
product fB of the filling factor (f) and the magnetic field strength (B)
can be determined with an accuracy better than 500G in relatively short
integration times if $v sin i < 20$ km/s. In a quick exploratory
observation we find that the lines in V410 Tau are too rotationally
broadened to allow determination of a magnetic field but find an upper
limit to fB of 2000G for the more slowly rotating weak line T Tauri star
Tap35 using a spectrum with a total integration time of only
16~minutes.}
% Here you write which journal accepted your paper, for example:
{ Accepted by A\&A }
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{Activity on the classical T~Tauri star
BP~Tauri}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ E. Gullbring$^1$, H. Barwig$^2$, P.S. Chen$^3$,
G.F. Gahm$^1$, M.X. Bao$^3$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Stockholm Observatory, S$-$133 36
Saltsj\"obaden, Sweden}\\
$^2$ {Universit\"ats-Sternwarte M\"unchen, Scheinerstrasse
1, D$-$81679 M\"unchen 80, Germany}\\
$^3$ {Yunnan Observatory, P.O. Box 110, Kumming, China}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: erik@astro.su.se}
%% Within the following brackets you place your text:
{We have made a detailed investigation of the
short-term variability in optical light (UBVRI) of the classical T
Tauri star BP~Tauri. Photometric data (in UBVRI) were collected from
Wendelstein Observatory, Germany in 1991, 1992 and 1993 with
time-resolutions down to 1 sec and, from binning, fluctuations with
total amplitudes down to a few milli-magnitudes could be
resolved. Additional observations (in UBV) were collected in
China. The total time of monitoring amounts to 135 hours.
The normal state of BP~Tau is that it stays completely
constant in brightness in all bands, or shows only very slow and
smooth changes during a night, to the limit of
detection. Brightenings, {\it events}, occurred on time-scales from 0.6
hours to a few hours but none of these reached a total amplitude $>$ 0.3
mag. in U. As a rule these events do not have the characteristic flare
profile as in the lightcurves of stellar surface flares. The total
optical energies of the events are a few times 10$^{35}$ erg, with a
relatively small spread. The energy distributions at peak flux can be
represented by black-body radiation. However, the inferred
temperature is very low, 7000 $-$ 8000 K, and not significantly different
from that derived for the background veiling. Hence, the events on BP
Tau are very different from normal stellar flares.
From power analysis of the time series, we conclude that there is no
power indicating frequent and short lasting phenomena, like surface
flares. In particular there is no signal in the U band. Such flares
would have been expected to be numerous in this high-sensitivity
survey, however, if BP~Tau had a magnetic surface activity comparable
to that of ordinary flare stars. Also, there is no tail in the
distribution of events towards smaller amplitudes and shorter
durations.
We show that the events of BP~Tau are consistent with
inhomogeneous mass infall from magnetically controlled accretion
between a circumstellar disk and a hot spot at the star. To account
for the constancy in temperature and the distribution of events over
frequency and amplitude, a model is proposed where the steady
accretion of BP~Tau is composed of small fragments which arrive close
to the star in a random fashion. By simulations we show that such a
flow can explain the smooth variations in the veiling and also the
sudden occurence of events. In this ``fractal'' model, each event is
composed of several superimposed fragments, which produce the
sometimes complex light profiles.
Finally, we find regular long-term variations with a period of 6.6
days, which is in line with (but not exactly) the periods found
by others.}
% Here you write which journal accepted your paper, for example:
{ Accepted by Astronomy \& Astrophysics}
\vspace{0.5cm}
\def\simgreat{\mathbin{\lower 3pt\hbox
{$\rlap{\raise 5pt\hbox{$\char'076$}}\mathchar"7218$}}} %> or of order
%% Between these brackets you write the title of your paper:
{\large\bf{Time Dependent Photodissociation Regions}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ David Hollenbach $^1$ \ and A. Natta $^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ { MS 245-3, NASA Ames Research Center, Moffett Field, CA 94035, USA}\\
$^2$ { Osservatorio Astrofisico di Arcetri,
Largo Enrico Fermi 5, I--50125 Firenze, Italy}
%% Within the following brackets you place your text:
{ We present theoretical models of the time dependent thermal and chemical
structure of molecular gas suddenly exposed to far ultraviolet (h$\nu <
13.6$ eV) radiation fields, and the consequent time dependent infrared
emission of the gas. We focus on the response of molecular hydrogen
(H$_2$) for cloud densities ranging from $n=10^3-10^6$ cm$^{-3}$ and
far ultraviolet (FUV) fluxes $G_0=10^3-10^6$ times the local FUV
interstellar flux. For $G_0/n>10^{-2}$ cm$^3$, the emergent H$_2$
vibrational line intensities are initially larger than the final equilibrium
values. The H$_2$ lines are excited by FUV fluorescence and by
collisional excitation in warm gas. Most of the H$_2$ intensity is
generated at a characteristic hydrogen column density
of $N\sim10^{21}$ cm$^{-2}$,
which corresponds to FUV optical depth of unity caused by dust opacity.
The time dependence of the H$_2$ intensities arises because the initial
abundances of H$_2$ at these depths is much higher than the equilibrium
values, so that H$_2$ initially competes more effectively with dust
in absorbing FUV photons. Considerable column densities
of warm, $T\sim 1000$ K,
H$_2$ gas can be produced by the FUV pumping of H$_2$ vibrational levels
followed by collisional deexcitation which transfers the energy to heat.
In dense ($n\simgreat 10^5$ cm$^{-3}$) gas exposed to high ($G_0\simgreat
10^4$) fluxes, this warm gas produces a 2-1S(1)/1-0S(1) H$_2$ line ratio
of $\sim 0.1$, which mimics the ratio found in shocked gas. In lower density
regions the FUV pumping produces a pure fluorescent ratio of $\sim 0.5$.
We also present estimates of the time dependent intensities of OI(6300 \AA),
SII(6730 \AA), FeII(1.64$\mu$m) and rotational OH and H$_2$O emission.
Potential applications include star forming regions, clouds near AGNs,
and planetary nebulae. We apply our models to five planetary nebulae and
conclude that only BD +30$^\circ$3639 shows evidence for enhanced H$_2$
emission due to (high) non-equilibrium H$_2$ abundances.
}
{Accepted by ApJ}
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Spectropolarimetry of the 3 micron ice feature towards the
Becklin-Neugebauer object}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ J.H. Hough$^1$, Antonio Chrysostomou$^1$, D. Messinger$^2$, D.C.B.
Whittet$^2$, D.K. Aitken$^1$, P.F. Roche$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Division of Physical Sciences, University of Hertfordshire, College
Lane, Hatfield, HERTS, AL10 9AB, UK} \\
$^2$ {Department of Physics, Applied Physics \& Astronomy, Rensselaer
Polytechnic Institute, Troy, NY 12180, USA} \\
$^3$ {Department of Astrophysics, University of Oxford, Keeble Road,
Oxford, OX1 3RH, UK} \\
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: jhh@star.herts.ac.uk OR acc@star.herts.ac.uk}
%% Within the following brackets you place your text:
{
We present spectropolarimetry of the 3.1 $\mu$m water-ice feature in the
Becklin-Neugebauer (BN) object in OMC-1 with substantially improved
spectral resolution and signal-to-noise over previous observations. The
well known increase in polarization within the ice feature is interpreted
in terms of a model for aligned graphite and silicate grains with ice
mantles. We identify polarization structure in the long wavelength (3.3 -
3.6 $\mu$m) wing of the ice profile, including a feature at 3.47 $\mu$m
which matches closely the spectroscopic feature discovered in several
protostars and attributed to carbonaceous material with diamond-like
structure. We also show, for the first time, the occurrence of a
systematic variation in the position angle of polarization across the ice
feature in BN, indicating systematic differences in the relative numbers
of core-mantle and unmantled grains along the line of sight, and a twist
in the magnetic field orientation. }
% Here you write which journal accepted your paper, for example:
{ Accepted by the Astrophysical Journal. To appear in the April 20 issue. }
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{A Near Infrared Study of the K3-50 Region of High Mass Star
Formation}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Eric M. Howard,$^1$ Judith L. Pipher,$^1$ William J. Forrest,$^1$ C.G. De Pree,$^{2,3}$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Physics and Astronomy, University of Rochester,
Rochester, NY 14627-0171, USA} \\
$^2$ {National Radio Astronomy Observatory, P.O. Box O, Socorro, NM
87801, USA} \\
$^3$ {Department of Physics and Astronomy, University of North
Carolina at Chapel Hill, NC 27599-3255, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: ehwd@sherman.pas.rochester.edu}
%% Within the following brackets you place your text:
{In an ongoing study of high mass star formation regions in the near
(1-5$\mu$m) infrared, we present J (1.2$\mu$m), H (1.65$\mu$m), K
(2.23$\mu$m), and L'' (3.81$\mu$m) broadband images as well as
Br$\gamma$ (n = 7$\rightarrow$4, 2.166$\mu$m) and Br$\alpha$ (n =
5$\rightarrow$4, 4.052$\mu$m) hydrogen recombination line images, and
3.29$\mu$m unidentified feature emission images of the K3-50 HII
regions K3-50A and K3-50B, at a plate scale of $\sim$0.''33 per pixel.
The Brackett line images are combined with radio data to map the line
of sight dust extinction to the compact HII region on small spatial
scales. The 3.29$\mu$m emission is found to overlap and extend beyond
the Br$\alpha$ and Br$\gamma$ emission into the photo-dissociation
region (PDR). We find clumps of dust extinction that may indicate a
cluster of stars is in the process of forming. The overall structure
of region K3-50A appears to be that of a rotating torus of dense gas
with a bipolar ionized gas outflow br! eaking through to the north
and south. }
% Here you write which journal accepted your paper, for example:
{ To appear in Ap.J., April 1, 1996 }
\vspace{0.5cm}
\def\msunyr{\ifmmode {\rm M_{\odot}\,yr^{-1}}\else $\rm M_{\odot}\,yr^{-1}$\fi}
%% Between these brackets you write the title of your paper:
{\large\bf{ A Magnetic Accretion Disk Model for the Infrared
Excesses of T Tauri Stars}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Scott J. Kenyon, Insu Yi, and Lee Hartmann }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{Harvard-Smithsonian Center for Astrophysics, 60 Garden St.,
Cambridge, MA 02138, USA}
%% Within the following brackets you place your text:
{We describe a magnetic accretion disk model for the infrared
colors of T Tauri stars in the Taurus-Auriga molecular cloud.
In this model, the stellar magnetic field truncates the
disk several stellar radii above the stellar photosphere;
material then flows along magnetic field lines and forms
a bright ring where the accretion stream impacts the star.
The model successfully reproduces the observations for
reasonable values of the magnetic field strength, 100--500 G;
the stellar rotational period, 4--10 d; and the
mass accretion rate, $10^{-8}$ to $10^{-6}$ \msunyr.
The truncation radius, $R_0$, lies well inside the corotation
radius, $R_c$. We estimate $R_0/R_c \approx$ 0.6--0.8 for
CTTS in our sample.
This result constrains models for the rotational evolution
and bipolar outflows of pre-main sequence stars.
Magnetic disk models make several testable predictions.
The near-IR colors should correlate with the stellar
magnetic field and the rotational period. The magnitude of
the near-IR veiling should strongly correlate with the
stellar rotational period. Strong CO emission or absorption
features should be present only in stars with high accretion
rates. Observations also discriminate between various types
of magnetic disk geometries if intrinsic stellar parameters --
such as the stellar radius and magnetic field strength -- are
well-known.}
% Here you write which journal accepted your paper, for example:
{Astrophys. J., April 20, 1996}
\vspace{0.5cm}
{\large\bf{Aperture Synthesis $^{13}$CO($J=1-0$) Observations of
the Molecular Gas around DG Tauri:
Evidence for a Dispersing Gas Disk}}
{\bf{ Yoshimi Kitamura$^1$, Ryohei Kawabe$^2$ \ and Masao Saito$^{2, 3}$ }}
$^1$ {Institute of Space and Astronautical Science, 3-1-1 Yoshinodai,
Sagamihara, Kanagawa 229, Japan}
\\ $^2$ {Nobeyama Radio Observatory, Nobeyama, Minamimaki-mura,
Minamisaku-gun, Nagano 384-13, Japan}
\\ $^3$ {Department of Astronomy, University of Tokyo, 2-11-16 Yayoi,
Bunkyo-ku, Tokyo 113, Japan}
{E-mail contact: kitamura@atom1.isaslan1.isas.ac.jp}
{We made aperture synthesis $^{13}$CO($J=1-0$) observations of the
molecular gas around a young star DG Tau, using the Nobeyama
Millimeter Array. We have detected the gas in the velocity range
$v_{\rm LSR} = 4.3 - 7.3$ km s$^{-1}$, and have revealed the velocity
structure of the gas with velocity resolution 0.43 km s$^{-1}$. The
molecular gas around DG Tau is found to have a disklike structure,
with the major axis perpendicular to the blueshifted optical jet
ejected from the star. The radius, mass, and inclination angle of the
disk are estimated to be $\sim$ 2800 AU, 0.03 $M_\odot$, and
40$^{\circ}$, respectively. It is noted that an expanding motion is
distinct in the disk. The expanding velocity is about 1.5 km
s$^{-1}$, which is larger than both the Kepler and free-fall
velocities around DG Tau. Since the mechanical luminosity of the
expanding motion is estimated to be 6 $\times$ 10$^{-4}$ $L_\odot$,
much smaller than the stellar luminosity of $\sim$ 1 $L_\odot$, the
expansion is possibly driven by the stellar wind from the central
star. The disk model for the expanding gas around DG Tau is quite
consistent with the structures of the reflection nebula and the
blueshifted optical jet that were observed around the star. It would
be reasonable to make the interpretation that the outer part of the
large gas disk around the star, or the disk-shaped remnant of the
envelope surrounding the star, is now being dispersed owing to the
stellar wind during the evolution of a large protostellar disk into a
compact protoplanetary one, because DG Tau has a flat spectral energy
distribution and is considered to be evolving from a protostar to a T
Tauri star.}
{ To appear in the 1996 January 20 issue of The Astrophysical Journal. }
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Near-infrared surface brightness observations of the
Thumbprint Nebula and determination of the albedo of interstellar grains}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Kimmo Lehtinen and Kalevi Mattila}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{Helsinki University Observatory, T\"ahtitorninm\"aki, P.O.\ Box
14, SF-00014, University of Helsinki, Finland}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: kimmo.lehtinen@helsinki.fi}
%% Within the following brackets you place your text:
{ We have made near-infrared J, H and K bandpass imaging of a small,
highly symmetric globule called the Thumbprint Nebula. At all these
wavelengths the globule shows a surface brightness higher than the
adjacent sky due to the radiation scattered by the globule. The
intensity of the observed surface brightness is interpreted in terms
of the scattering properties, i.\ e.\ albedo $a$ and the form of the
scattering function (phase function asymmetry parameter $g$) of the
dust particles. Monte Carlo calculations for a spherical cloud have
been used to solve the radiation transfer problem for different values
of $a$ and $g$.
The all-sky measurements of the DIRBE (Diffuse InfraRed Background
Experiment) instrument aboard the COBE$^{1}$ (COsmic Background
Explorer) satellite were used to calculate the galactic radiation
field incident on the globule at 1.26 and 2.16\,$\mu$m, while at
1.66\,$\mu$m an interpolation has been used.
The values of $a$ and $g$ can not be determined separately, but the
value of $a$ is nearly independent of $g$ for probable values of $g$
($0.0 < g < 0.8$). If it is assumed that the observed surface
brightness is due solely to the scattered light then the grain albedo
is $0.7$ at 1.26 and 1.66\,$\mu$m, and $0.6$ at 2.16\,$\mu$m, for $0.0
< g < 0.8$.
The reddening of the stars shining through the globule is used to
determine the radial dust density distribution. The dust density
distribution is found to be more centrally peaked than the density
distribution of molecular gas.
% Here you write which journal accepted your paper, for example:
{ Accepted by Astronomy \& Astrophysics }
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Mid-Infrared Imaging of Young Stellar Objects}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Michael C. Liu$^1$, James R. Graham$^1$, A. M. Ghez$^2$, M.
Mexiner$^3$, C. J. Skinner$^4$, Eric Keto$^4$, Roger Ball$^4$, J.
F. Arens$^5$,\ and J. G. Jernigan$^5$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Astronomy, University of California, Berkeley,
CA 94720, USA} \\
$^2$ {Department of Astronomy, University of California, Los
Angeles, CA 90024, USA} \\
$^3$ {Department of Astronomy, Univerisity of Illinois,
Urbana-Champaign, IL 61801, USA} \\
$^4$ {Institute of Geophysics and Planetary Physics, Lawrence
Livermore National Laboratory, Livermore, CA 94551, USA} \\
$^5$ {Space Science Laboratory, University of California, Berkeley,
CA 94720, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: mliu@astro.berkeley.edu}
%% Within the following brackets you place your text:
{
We present arcsecond resolution mid-infrared (8--13
$\mu$m) images and photometry of four young stellar objects
(YSOs)~--- L1551-IRS5, HL~Tau, AS~205, and AS~209 (V1121~Oph)~---
taken with the Berkeley Mid-Infrared Camera. For AS~205, a known T
Tauri binary, we also present near-infrared JHK images and
HKL$^{\prime}$ speckle imaging data. All three single stars are
unresolved in our mid-IR images, consistent with current models of
the circumstellar material associated with these objects.
Our data is the first to resolve in the mid-IR both components of
the close binary AS~205 (projected separation $\sim$1.3$^{\prime
\prime}$ (210~A.U.)). Both stars are classical T Tauri stars and
possess the 9.7 $\mu$m silicate feature in emission. AS~205~N is
the IR brighter star in our data while published observations find
it to be the optically fainter star. Assuming the IR excesses of
both components arise from circumstellar disks, we find the
emitting regions (the inner few A.U.) of the disks to be optically
thick in the mid-IR. Pre-main sequence evolutionary models suggest
the AS~205 system is non-coeval; we discuss possible explanations
for this result and comment on the evolutionary status of this
young binary.
All of our objects, except perhaps AS~205~South, exhibit
changes in their mid-IR flux in measurements separated by intervals
of days up to many years; the variations range from 30--300\%. For
the classical T Tauri stars AS~205~North and AS~209, the magnitude
of the changes seems to discount the possibility the mid-IR
variations have the same origin as the optical and near-IR
variability of T Tauri stars, namely accretion-related features on
or near the stellar photosphere. We speculate that the cause of
the variability lies in the accretion disks of these objects; the
data suggest disk accretion rate fluctuations of nearly an order of
magnitude. The existence of large mid-IR variability argues that
simultaneous multiwavelength observations are needed for a proper
analysis of YSO spectral energy distributions.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by the Astrophysical Journal }
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Spectroscopy of Possible H$\alpha$ Emission Stars in Regions of
High Galactic Latitude Molecular Clouds}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Eduardo L. Mart\'\i n$^1$ and Maria Kun$^2$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Instituto de Astrof\'{\i}sica de Canarias, 38200 La Laguna,
Tenerife, Spain} \\
$^2$ {Konkoly Observatory, P.O. Box 67, H-1525 Budapest, Hungary}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: ege@iac.es}
%% Within the following brackets you place your text:
{ We present mid-resolution spectroscopic observations of 63 faint
(V=12--16) stars identified by Kun~(1992) as H$\alpha$ emission
candidates in an objective prism survey of several high galactic
latitude molecular clouds. Only 4 stars in our sample (6\%) are bona
fide T Tauri stars on the basis of their strong Li absorption and
H$\alpha$ emission features. They have late M spectral types
(M4--M5.5) and two of them form a visual binary with separation
$\sim$7". The new T Tauris are associated with the L\,134 molecular
complex, the northernmost extension of the Scorpio -- Ophiuchus star
forming region, which has been traditionally considered as a non-star
forming region.
In the other high latitude clouds surveyed by Kun 1992, we have not
found any T Tauri star in our follow-up spectroscopy. Most of the
observed stars ($\sim$80\%) are late type dwarfs without detectable
H$\alpha$ emission in our spectra. Eight stars are M-dwarfs with
H$\alpha$ in emission, but no detectable Lithium absorption. They could be
post T Tauri stars or older dMe stars; more data is necessary in order
to establish their evolutionary status. Our results show that Kun
(1992) was able to detect weak H$\alpha$ emission lines (down to equivalent
width of $\sim$ 1.5 \AA ) in faint stars near the plate magnitude
limit (V$\sim$16), but in many cases plate defects, absorption bands
and/or overlying stars were taken as possible H$\alpha$ emission. In this
paper we correct Kun's previous indication that there may be numerous
young stars associated to high latitude molecular clouds, and we
severely constrain the presence of a population of T Tauri stars in
these clouds. We note that none of our four T Tauri stars is located
in an isolated translucent molecular cloud. }
% Here you write which journal accepted your paper, for example:
{ Accepted by A \& A Supplement Series}
\vspace{0.5cm}
\def\kms{km~s$^{-1}$ }
\def\kmsn{km~s$^{-1}$}
\def\smasn{M$_\odot$}
\def\smas{M$_\odot$ }
\def\arcsec{$^{\prime\prime}$ }
\def\arcsecn{$^{\prime\prime}$}
%% Between these brackets you write the title of your paper:
{\large\bf{
The Location of Extremely High Velocity HCO$^+$ in the HH 7-11
Outflow
}}
%% Here comes the author(s) of the paper, please indicate within
%% $^...$
%% the number which corresponds to the institute of each author.
{\bf David M. Mehringer }
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{University of Illinois, Department of Astronomy, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for
%% example:
{E-mail contact: dmehring@sirius.astro.uiuc.edu}
%% Within the following brackets you place your text:
{ In order to determine the location of extremely high velocity
HCO$^+$ emission in the HH 7-11 outflow, BIMA array observations of
the $J$=1$\rightarrow$0 transition with 11\arcsec $\times$ 8.9\arcsec
angular resolution were carried out. Two spatially unresolved clumps
with average velocities $\sim$40 \kms blueward of the ambient material
are detected. The two clumps are projected $}{\sim}$ $10^4$ years and show a correlation between the
bolometric luminosity and the millimeter continuum flux, which we call
the ``Outflow Strip'': this correlation spans more than three orders
of magnitude in luminosity. We suggest that the Outflow Strip
originates in the deuterium burning process and that the protostars
burn the majority of their deuterium while on the Outflow Strip.
There is also good evidence that at the end of their lifetime on the
Outflow Strip, the embedded outflow sources become visible Pre Main
Sequence (hereafter PMS) stars with outflows. The outflow mechanical
luminosity is also found to be better correlated to the mass of the
disk/envelope system than to the central object luminosity. }
%
% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. \& Astrophys.}
%
\vspace{0.5cm}
{\large\bf{Physics of Accretion onto Young Stars : I Parametric Models}}
{\bf{ Lionel Siess \ and Manuel Forestini }}
{Observatoire de Grenoble, Laboratoire d'Astrophysique,
Universit\'e Joseph Fourier, B.P.53X, F-38041, Grenoble Cedex, France \\
E-mail contact: siess@gag.observ-gr.fr}
{The article will present the influence of accreting
material on the structure of young stars. We model
accretion through a formalism based upon the Richardson
criterion which relates the power of buoyancy forces
to the kinetic energy of turbulence. In our models we
assume that in radiative regions matter is close to
marginal stability and we generalize this formalism to
convective zones. We take into account the angular
momentum as well as the thermal and chemical properties
of the accreted matter.
We present figures that depict the profile of mass
deposition in the star. We study parametrically peculiar
aspects of the accretion physics such as how energy is
transported through the accretion process or what is the
effect of chemical composition differences between the star
and the accretion disk or what is the result of accreting
more or less angular momentum.
The models show that very rapidly the accreted matter
can reach the convective zone and eventually can be
dragged to the center of the star.
This approach will be soon incorporated into evolutionary
models of young stellar objects.}
{ Accepted by Astronomy and Astrophysics}
\newpage
{\large\bf{ Observation of a Lunar Occultation of T Tau}}
{\bf{ M. Simon,$^{1}$ A.J. Longmore,$^2$ M.A. Shure,$^{3}$ and
A. Smillie$^2$ }}
$^1$Astronomy Prog., SUNY, Stony Brook, NY 11794-2100 \\
$^2$Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, Scotland,
United Kingdom\\
$^3$Center for High Angular Resolution Astronomy, Georgia State Univ.,
Atlanta, GA, 30303-3083, USA
{E-mail contact: msimon@sbast1.ess.sunysb.edu}
{We observed the 16 December 1994 (UT) lunar occultation of the binary
system T Tau in the infrared K and L' bands. T Tau N, the visible light star,
and T Tau S, the IR luminous companion, appeared unresolved along the direction
of the occultation. At L', both objects are smaller than 3 AU. At K, T Tau N
and S are smaller than 1 AU. The natural interpretation is that both
components are stellar and that the extinction along our line of sight
to T Tau S is greater than to T Tau N. At the time of the occultation,
the K-band flux of T Tau S had decreased to nearly the value it had before
the flare that began in the late 1980's while the L'-band flux was still
elevated; this flux decrease with time supports Ghez {\it et al.}'s (1991)
suggestion that T Tau S experienced a FU Orionis-like outburst.}
{ Accepted by Ap. J. Letters}
\vspace{0.5cm}
\def\simgreat{\mathbin{\lower 3pt\hbox
{$\rlap{\raise 5pt\hbox{$\char'076$}}\mathchar"7218$}}} %> or of order
%% Between these brackets you write the title of your paper:
{\large\bf{Infall in Herbig Ae/Be Stars: What the Na D Lines Tell Us}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{C. Sorelli$^1$, V.P. Grinin$^2$, A. Natta$^3$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ { Dipartimento di Astronomia, Universit\`a di Firenze,
Largo Enrico Fermi 5, I--50125 Firenze, Italy}\\
$^2$ { Crimean Astrophysical Observatory,
Crimea, 334413 Nauchny, Ukraine}\\
$^3$ { Osservatorio Astrofisico di Arcetri,
Largo Enrico Fermi 5, I--50125 Firenze, Italy}
%% Within the following brackets you place your text:
{ This paper discusses the origin of the redshifted absorption
components observed in the Na D lines of some Herbig Ae/Be stars. We
have computed non-LTE models of the thermal and ionization structure
of gas clouds of different density, column density and chemical
composition, from the solar one to that typical of CI-chondrites. The
redshifted absorption lines can only form in small, dense, infalling
gas clumps at distances $\leq$10 R$_{\star}$ from the star. If the
gas has solar chemical composition, then the clump size must be
$L\approx 10^{11}$ cm (about R$_{\star}$) and the density $n_H\geq
3\times 10^{12}$ cm$^{-3}$. These conditions can be produced at the
base of a column of gas falling into the star from a circumstellar
accretion disk along magnetic lines. In this case, an accretion rate
$\dot M_{acc}\geq 3\times 10^{-7}$ M$_{\odot}$yr$^{-1}$ and a stellar
magnetic field of about 600 Gauss are required. As the gas
metallicity increases, less dense clouds are required to fit the Na D
observations. In the extreme case of a gas cloud resulting from the
evaporation of CI-chondrite meteorites, it is $n_H\geq 5\times 10^8$
cm$^{-3}$, $L\approx 10^{11}$ cm. The mass of the cloud is therefore
of the order of $10^{20}$ gr, and the parental body must have a radius
of 20 km at least. These results show that both scenarios, i.e.,
magnetospheric accretion and evaporation of star-grazing planetesimal
bodies, are in principle possible.}
% Here you write which journal accepted your paper, for example:
{ Accepted by A\&A}
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Photon Heating of Envelopes around Young Stellar Objects:
An Explanation for CO J=6--5 Emission}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Marco Spaans$^{1,2}$, Michiel R.\ Hogerheijde$^1$, Lee G.\
Mundy$^3$, and Ewine F.\ van Dishoeck$^1$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Sterrewacht Leiden, P.O.\ Box 9513, 2300 RA Leiden, The Netherlands} \\
$^2$ {currently at: Dept. of Physics and Astronomy, The Johns
Hopkins University, Baltimore, MD 21218, USA} \\
$^3$ {Astronomy Department, University of Maryland, College Park, MD
20742, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: spaans@pha.jhu.edu, michiel@strw.leidenuniv.nl}
%% Within the following brackets you place your text:
{We propose that the narrow $^{12}$CO and $^{13}$CO J=6--5 emission
observed toward many low mass young stellar objects is produced in
molecular material in the circumstellar envelope which is heated by
the 10,000 K radiation field generated in the inner part of the
accretion disk. Ultraviolet photons traveling through the biconical
cavity evacuated by the bipolar outflow are scattered by dust grains
present in the low density material in the cavity. These photons are
not energetic enough to photodissociate H$_2$ and CO, but can heat the
envelope surrounding the cavity. The temperature structure and the CO
excitation of this photon-dominated region are computed using 2-D
Monte Carlo methods. It is found that the material is heated up to a
few hundred K close to the cavity wall, and that the observed
low--velocity mid--J CO emission can be well explained by our model
for a wide range in envelope density and stellar luminosity. Emergent
CO spectra are compared to observations of the embedded low mass YSO
IRAS~04361+2547 (TMR-1).}
% Here you write which journal accepted your paper, for example:
{ Accepted by The Astrophysical Journal, Letters (December 1995) }
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Magnetic Fields in Cometary Globules I: \mbox{CG 22}}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ T.K.Sridharan$^{1}$, H.C.Bhatt$^{2}$ \ and Jayadev Rajagopal$^{1}$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Raman Research Institute, Bangalore 560 080, India}\\
$^2$ {Indian Institute of Astrophysics, Bangalore 560 034, India}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: tks@rri.ernet.in}
%% Within the following brackets you place your text:
{We report first results from a program to study magnetic fields in
Cometary Globules (CGs). These are clouds near massive stars showing a
head-tail morphology. Linear optical polarisation measurements on stars
seen projected on CG 22 in the Gum-Vela region are presented. A majority
of the stars seen within the boundary of the cloud show a polarisation of
$\sim$ 1\% with the electric field vector oriented parallel to the tail
whereas those outside the boundary either show small polarisation with
position angles parallel to the Galactic plane or no polarisation within
the errors of our measurements. If the polarisation is due to dust grains
aligned by magnetic field our results imply that the field in CG 22 is
parallel to its tail. A rough estimate of the field strength ($\sim$ 30
$\mu$G) indicates that it may be important for the dynamics of the cloud.
These results support the idea that magnetic fields play a role
in producing the structures seen in the tails of the CGs.
We suggest that the alignment of the magnetic field could only have been
caused by the same process that shaped the tails. We also comment on the
implications of the polarisation detected in the light from the star Wra
220, a T-Tauri star believed to have formed in the head of CG 22.}
% Here you write which journal accepted your paper, for example:
{ Accepted by MNRAS}
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Global Evolution of Solid Matter in Turbulent Protoplanetary
Disks. I. Aerodynamics of Solid Particles}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{T. F. Stepinski $^1$ \ and P. Valageas $^2$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Lunar and Planetary Institute, 3600 Bay Area Blvd., Houston,
TX 77058, USA } \\
$^2$ {Service de Physique Th\'eorique, CEN Saclay, 91191 Gif-sur-Yvette,
France }
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: tom@lpis54.jsc.nasa.gov}
%% Within the following brackets you place your text:
{The problem of planetary system formation and its subsequent
character can only be addressed by studying the global evolution
of solid material entrained in gaseous protoplanetary disks. We
start to investigate this problem by considering the space-time
development of aerodynamic forces that cause solid particles to
decouple from the gas. The aim of this work is to demonstrate that
only the smallest particles are attached to the gas, or
that the radial distribution of the solid matter has no momentary
relation to the radial distribution of the gas. We present the
illustrative example wherein a gaseous disk of 0.245 $M_{\odot}$
and angular momentum of $5.6\times 10^{52}$ g cm$^2$ s$^{-1}$ is
allowed to evolve due to turbulent viscosity characterized by either
$\alpha=10^{-2}$ or $\alpha=10^{-3}$. The motion of solid particles
suspended in a viscously evolving gaseous disk is
calculated numerically for particles of different sizes. In
addition we calculate the global evolution of single-sized,
noncoagulating particles. We find that particles smaller than
0.1 cm move with the gas; larger particles have significant radial
velocities relative to the gas. Particles larger then 0.1 cm but
smaller than $10^3$ cm have inward radial velocities much larger
than the gas, whereas particles larger than $10^4$ cm have inward
velocities much smaller than the gas. A significant difference in
the form of the radial distribution of solids and the gas develops
with time. It is the radial distribution of solids, rather than
the gas, that determines the character of an emerging planetary
system.}
%Here you write which journal accepted your paper, for example:
{Accepted by Astron. \& Astrophys.}
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{Escape of T Tauri stars from young stellar systems}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{Michael F. Sterzik$^{1,2}$ \ and Richard H. Durisen$^{1,3}$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Max Planck Institut f\"{u}r extraterrestrische Physik,
85740 Garching bei M\"{u}nchen, Germany} \\
$^2$ {Theoretische Astrophysik, Universit\"at T\"ubingen,
72076 T\"ubingen, Germany} \\
$^3$ {Department of Astronomy, SW319, Indiana University, Bloomington,
Indiana 47405, U.S.A.}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: sterzik@mpe-garching.mpg.de}
%% Within the following brackets you place your text:
{The decay of nonhierarchical
few-body systems ($N<10$) is examined by direct numerical integration
to determine statistically
how size, shape, $N$, and rotation state
influence the distribution of escape speeds for ejected stars.
The initial conditions are chosen to represent realistic configurations
for young stellar objects at the end of the accretion phase in
fragmented protostellar clouds.
If we adopt typical properties for molecular cloud cores and
assume system sizes deduced from isothermal collapse calculations,
we find that more than 60\% of the escapers have speeds $> 3$ km/s.
We propose that high-velocity stars
produced during the decay of young multiple star systems
contribute significantly to the halo of
weak-line T Tauri stars recently discovered
around star forming regions by the ROSAT
all-sky X-ray survey.}
% Here you write which journal accepted your paper, for example:
{ Accepted by A\&A Letters }
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Young Star Clusters in Bright-Rimmed Clouds:
Small-Scale Sequential Star Formation?}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ K. Sugitani$^1$, M. Tamura$^2$ \ and K. Ogura$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {College of General Education, Nagoya City University, Mizuho-ku,
Nagoya 467, Japan} \\
$^2$ {National Astronomical Observatory, Osawa 2-21-1, Mitaka, Tokyo 181,
Japan} \\
$^3$ {Kokugakuin University, Higashi, Shibuya-ku, Tokyo 150, Japan}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: sugitani@nsc.nagoya-cu.ac.jp}
%% Within the following brackets you place your text:
{A J/H/K imaging survey has been made for 44 bright-rimmed clouds
associated with IRAS point sources of Sugitani et al. (1991). We have
found small clusters of near-infrared sources having YSO colors in some
of these objects, and most of the cluster members are considered to be
older than the IRAS point sources and to be pre-main sequence stars
such as T Tauri stars. In at least 6 bright-rimmed clouds, the clusters
are elongated towards the bright rim tip or the exciting star(s) of
the bright rim with the IRAS sources situated near the other end.
There is a tendency that bluer (i.e., older) stars are located closer to
the exciting star(s) and redder (i.e., younger) stars closer the IRAS sources.
This asymmetric distribution of the cluster members strongly suggests
small-scale sequential star formation or propagation of star formation
from the side of the exciting star(s) to the IRAS position in a few $10^5$yr
time, due to the advance of the shock caused by the UV radiation from
the exciting star(s).}
% Here you write which journal accepted your paper, for example:
{ Accepted by Ap. J. Letters, Dec. 1, 1995 issue }
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Gap Formation in Protoplanetary Disks}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Taku Takeuchi$^{1,2}$, Shoken M. Miyama$^2$ \ and D. N. C. Lin$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Department of Astronomical Science, The Graduate University for
Advanced Studies, Mitaka, Tokyo 181, Japan} \\
$^2$ {National Astronomical Observatory, Mitaka, Tokyo 181, Japan} \\
$^3$ {University of California Observatories/Lick Observatory,
University of California, Santa Cruz, CA95064, USA}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: takeuchi@yso.mtk.nao.ac.jp}
%% Within the following brackets you place your text:
{Evolution of a protoplanetary disk under the tidal interaction
between the disk and an embedded protoplanet is analyzed with a self
consistent WKB approximation. We assume that the protoplanetary disk
is infinitesimally thin and non-self-gravitating and that the
protoplanet's orbit is circular. The protoplanet excites density
waves at its Lindblad resonances. As they propagate throughout the
disk, these waves carry a flux of angular momentum which is eventually
deposited into the gas at the locations where the waves are dissipated
viscously. Protoplanets with a sufficiently large mass can induce the
formation of a gap in the disk. The size of the gap and the structure
of the disk are determined by the wave propagation length scale which
is a decreasing function of viscosity. For small effective viscosity,
density waves propagate to inner regions near the protostellar
surface. Using an $\alpha$ prescription, we find that a Jupiter-mass
protoplanet can lead to the removal of the inner disk if $\alpha \le 3
\times 10^{-4}$. For larger values of $\alpha$, the surface density
in the disk surrounding the gap is adjusted in a manner such that the
rapid orbital evolution by the protoplanet is prevented. We also
inferred that $\alpha \sim 1.7 \times 10^{-2}$ in the disk around the
binary T Tauri star GW Ori, based on the gap size derived from the
observational data.}
% Here you write which journal accepted your paper, for example:
{ Accepted by ApJ (To be published Apr. 1, 1996)}
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{ First observations of the water vapour
line at 557 GHz from the interstellar medium}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ J.~Tauber$^1$, G.~Olofsson$^2$, G.~Pilbratt$^1$, L.~Nordh$^2$,
and U. Frisk$^{1,3}$ }}
%
%% First Author$^1$, Second Author$^2$ \ and Third Author$^3$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {ESA Astrophysics Division, Space Science Department, ESTEC,
P.O. Box 299, NL\,--\,2200~AG Noordwijk, The Netherlands} \\
$^2$ {Stockholm Observatory, S\,--\,13336 Saltsj\"obaden, Sweden} \\
$^3$ {Present address: Swedish Space Corporation, P.O. Box 4207,
S\,--\,17104 Solna, Sweden }
%$^1$ {European Southern Observatory, Casilla 19001, Santiago 19, Chile} \\
%$^2$ {Cerro Tololo Inter-American Observatory, National Optical Astronomy
% Observatories, Casilla 603, La Serena, Chile} \\
%$^3$ {Las Campanas Observatory, Carnegie Inst. of Washington, Casilla
% 601, La Serena, Chile}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: jtauber@astro.estec.esa.nl}
%reipurth@eso.org}
%% Within the following brackets you place your text:
%{This is the abstract of your paper}
{We report the first results of PIROG 7, a balloon-borne platform
equipped with a 60\ cm telescope and a heterodyne receiver designed
for observations of the 557 GHz ($1_{10}\rightarrow1_{01}$) line of
ortho-H$_2$O. We describe the experiment, atmospheric transmission
measurements, and astronomical observations of Orion. The lack of
broad, centrally peaked line emission in this source, compared to the
recently detected line of H$_{2}$$^{18}$O at 548 GHz, indicates that
the abundance of water is large and its emission optically thick. On
the other hand, a weak and narrow absorption feature was detected
toward Orion. While the signal-to-noise ratio of the observed
absorption is such that it should only be considered as a tentative
detection at the present moment, the result is consistent with the
available information on the physical characteristics of the gas in
this region. The feature can be interpreted as the result of
absorption by a foreground ridge-like component of bright and wide
emission arising from the warm gas in the high-velocity core of
Orion.}
% Here you write which journal accepted your paper, for example:
%{ Accepted by Astron. J. }
{ Accepted by Astronomy \& Astrophysics }
\vspace{0.5cm}
{\large\bf{On the stability of an accretion disc containing a toroidal
magnetic field}}
{\bf{ Caroline Terquem \ and John C.B. Papaloizou}}
{Astronomy Unit, School of Mathematical Sciences, Queen Mary and
Westfield College, University of London, Mile End Road, London
E1 4NS, UK}
{E-mail contact: C.Terquem@qmw.ac.uk, J.C.B.Papaloizou@qmw.ac.uk}
{We study the stability of an accretion disc with an embedded toroidal
magnetic field to general perturbations. Disc models are considered in
which the equilibrium variables depend on both the radial and vertical
coordinates. We consider the full global problem in which the disc may
be in the form of a narrow annulus or occupy a significant radial
extent. Perturbations with azimuthal mode number $m$ in the range zero
up to the ratio of the radius to disc semi-thickness are considered.
Discs containing a purely toroidal magnetic field are always found to
be unstable. We find spectra of unstable modes using local
techniques. In the absence of dissipation, these modes may occupy
arbitrarily small scales in the radial and vertical directions. One
class of modes is driven primarily by buoyancy, while the other is
driven by shear independently of the equilibrium stratification. The
first type of instability predominates if the field is large, while
the second type predominates if the field is weak and the underlying
medium is strongly stable to convection.
We also investigate stability by solving the initial value problem for
perturbations numerically. We find, for our disc models, that local
instabilities predominate over any possible global instability. Their
behaviour is in good accord with the local analysis. The associated
growth rates become just less than the orbital frequency when the
ratio of magnetic energy density to pressure reaches about ten
percent.
Instabilities of the kinds discussed here may provide a mechanism for
limiting the growth of toroidal fields in dynamo models of accretion
discs.
}
{ Accepted by MNRAS }
\newpage
{\large\bf{Tidally-induced Warps in T~Tauri Discs. II. A Parametric Study of
Spectral Energy Distributions}}
{\bf{ Caroline Terquem$^{1,2}$ \ and Claude Bertout$^2$ }}
$^1$ {Astronomy Unit, School of Mathematical Sciences,
Queen Mary and Westfield College, Mile End Road, London E1 4NS,
UK} \\
$^2$ {Laboratoire d'Astrophysique, Observatoire de Grenoble,
Universit\'e Joseph Fourier/CNRS, BP 53X,
38041 Grenoble Cedex, France}
{E-mail contact: C.Terquem@qmw.ac.uk, bertout@gag.observ-gr.fr}
{We compute here the spectral energy distribution (SED) of warped
T~Tauri discs in a general way. In a previous paper (Terquem~\&
Bertout~1993) we analytically calculated, in a linear aproximation,
the response of a circumstellar disc to tidal forces due to a stellar
companion in a non-coplanar young binary system. Here, we consider
tidally-induced warps of larger amplitude, and we use these previous
results to parametrize the disc deformation. We then compute the
energy emitted in a given direction by the system of the warped disc
and central star, taking into account shadowing effects.
We find that the parametrized warp model produces a broad variety of
synthetic SEDs. Some of them are comparable to those of T~Tauri stars
with infra-red excess (Class II sources), whereas others resemble
Class~I protostellar sources. By comparing models with actual
observations of both a T~Tauri star with high spectral index and a
Class~I source, we find that the derived warp and disk parameters are
not unrealistic, and we conclude that tidal interactions in T~Tauri
binary systems with intermediate separations must play a role in
shaping the SEDs of these stars.}
{ Accepted by MNRAS}
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Orbital motion of DF Tauri from speckle interferometry}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{E.\ Thi\'ebaut$^{1}$, Y.\ Balega$^{2}$, I.\ Balega$^{2}$, I.\
Belkine$^{1,2}$, J.\ Bouvier$^{4}$, R.\ Foy$^{1}$, A.\ Blazit$^{3}$ \
and D.\ Bonneau$^{3}$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^{1}$ {Observatoire de Lyon, CNRS UMR 142, 69561 St-Genis-Laval Cedex,
France}\\
$^{2}$ {Special Astrophysical Observatory, Nizhnij Arkhyz, Zelenchuk
region, Karachai-Cherkesia, 357147 Russia}\\
$^{3}$ {Observatoire de la C\^{o}te d'Azur, D\'{e}partement A. Fresnel,
CNRS URA 1361, France}\\
$^{4}$ {Observatoire de Grenoble, CNRS URA 708, France}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: thiebaut@obs.univ-lyon1.fr}
%% Within the following brackets you place your text:
{We report the evidence of the orbital motion of the binary star
DF~Tau. This result is obtained from visible speckle interferometry
and uses lunar occultations of Chen et al. (1990, ApJ {\bf{357}},
224). It is the first step towards a direct determination of the
dynamical mass of this young system. The portion of the orbit covered
between the epochs of observation is still too small ($\sim\!10\%$) to
allow precise derivation of the orbital elements. We however provide a
first estimate of the mass of the system as being
$2.8\!\pm\!1.5\,M_\odot$. We investigate the incidence of the
binarity of DF~Tau on the modeling of its spectral energy distribution
and discuss the nature of the components.}
%% Here you write which journal accepted your paper, for example:
{Accepted by Astron. Astrophys. Lett.}
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{ The Molecular Core Associated with HH25-26: Contraction
or Expansion }}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Lourdes Verdes-Montenegro$^1$ \ and Paul T. P.
Ho$^2$ }}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ { Instituto de Astrof\'{\i}sica de Andaluc\'{\i}a, CSIC,
Apdo. 3004, 18080
Granada, Spain} \\
$^2$ { Harvard-Smithsonian Center for Astrophysics, Cambridge, Mass.,
USA}
%% Within the following brackets you place your text:
{
We mapped the star formation region HH25-26 IR in the NH$_3$(1,1) and
(2,2) transitions using the VLA in its D configuration. The study has
been made with 5$^{\prime\prime}$ angular resolution and
0.3~km~s$^{-1}$ velocity resolution.
As has been seen before, there is an elongated NH$_3$ core which lies
perpendicular to the molecular outflow as traced in high velocity CO
emission. In this experiment, the NH$_3$ core is resolved, showing a
central cavity and a number of distinct velocity features. Heating is
seen where the velocity features overlap spatially, and on the edges
of the cavity, which is also seen as a reflection nebula with
evidences for shock excitation. We have also detected what appears to
be a new 1.3 cm continuum source on the wall of the cavity, associated
with a 2.2$\mu$ point source and jet-like structure. It is not clear
at this time whether this is truly continuum emission or high velocity
ammonia emission. The overall kinematics is complicated. A velocity
gradient can be seen, together with the signatures for expanding or
contracting motions.
We consider here two possible models: a) a disk or ring structure,
slowly rotating and contracting, and b) an expanding cavity. }
% Here you write which journal accepted your paper, for example:
{ Accepted by A \& A }
\vspace{0.3cm}
\def\eq {\raise1.0pt\hbox{$\scriptstyle=$}}
\def\hii {H\,{\sc ii} }
\def\pam {.\hskip-2pt$^\prime$}
%% Between these brackets you write the title of your paper:
{\large\bf{The Structure of the IC\,1396 Region}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{H.\,Weikard\,$^{1,2}$, J.G.A.\,Wouterloot\,$^2$,
A.\,Castets\,$^1$, G.\,Winnewisser\,$^2$, and K.\,Sugitani\,$^3$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Groupe d'Astrophysique, Observatoire de Grenoble,
B.P.\,53\,X, 38041 Grenoble CEDEX, France } \\
$^2$ {I.~Physikalisches Institut, Universit\"at zu K\"oln,
Z\"ulpicher Stra{\ss}e 77, 50937 K\"oln, FRG } \\
$^3$ {College of General Education, Nagoya City University, Mizuho-ku,
Nagoya 467, Japan}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: weikard@gag.observ-gr.fr}
%% Within the following brackets you place your text:
{
We have made an extensive study of the molecular clouds associated with
the \hii region IC\,1396 in the rotational transitions $J$\eq1$-$0 and
$J$\eq2$-$1 of $^{12}$CO and $^{13}$CO and $J$\eq3$-$2 of $^{12}$CO
with an average spatial resolution of \hbox{2\pam 5} and an average sampling
of about \hbox{2\pam 0}, in order to get information on its structure and
evolution.
On the basis of our observations, which cover an area of more than
6~deg$^2$, we can classify the molecular clouds into those directly
associated with the ionizing O6.5V~star HD\,206267, producing the
bright-rimmed clouds, and the cold gas along the line of sight, which
is mainly foreground material. The bright-rimmed clouds show the
presence of warmer molecular gas through higher \hbox{$^{12}$CO
(2$-$1)/(1$-$0),}
\hbox{$^{13}$CO (2$-$1)/(1$-$0)} and \hbox{$^{12}$CO (3$-$2)/(2$-$1)} line
ratios than the cold foreground gas. The warm clouds form roughly a
shell-like arrangement with a diameter of~25 to 40~pc around
HD\,206267 (though most are slightly closer to the Sun than the
O~star), and they seem to be the remainder of the now dispersing
molecular cloud which gave birth to the O6.5~star and the star cluster
Tr\,37 associated with it. All bright-rimmed clouds show internal
structure on all size scales, including bipolar outflows. Optical,
FIR (IRAS 12~to 100~$\mu$m) and CO maps are in close agreement over
the whole region, especially for the bright-rimmed clouds: Exceptions
are some optically bright (ionized) regions, which show FIR, but no
CO~emission, and the cold foreground clouds, which are very weak at
FIR wavelengths.
The entire mass of the mapped IC\,1396 region is estimated to be
12\,000~M$_\odot$, which is composed of molecular (4000~M$_\odot$),
atomic (5000~M$_\odot$), and ionized material (3000~M$_\odot$) in
nearly equal amounts. The masses of the bright-rimmed clouds range
from a few to several 100~M$_\odot$. }
%% Here you write which journal accepted your paper, for example:
{ Accepted by Astron. Astrophys. }
\vspace{0.3cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Discovery of New Wide Binary Infrared Protostars}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Jo\~{a}o Lin Yun}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
{Departamento de F\'{\i}sica, Universidade de Lisboa, Campo Grande,
Ed. C1, 1700 Lisboa, Portugal}
%% Within the following brackets you place your text:
{
We present observational evidence based on near-infrared array imaging of what
could be not only candidates for infrared protostars (Class~I objects) but also
for wide binary infrared protostars found in Bok globules.
The extremely early evolutionary stage of the objects is confirmed by the
following facts: {\it i)} The objects are not present on the Palomar prints nor
on optical CCD images reaching 19$^{\rm th}$ magnitude in the I-band;
{\it ii)} The objects exhibit very red colors. Values of $(J-H)$ and $(H-K)$ are
consistent with those of very embedded Class~I objects surrounded by
circumstellar dust emission.
The binary character of these pairs of objects is indicated by the following
facts: {\it i)} At 2.2 $\mu$m, each pair appears to reside in common nebulosity
indicating that they could be physically associated;
{\it ii)} The separation between the stars in each pair is about 10 arcsec
and they appear isolated within globule cores extending for several
arcminutes in diameter.
The orientations of their associated molecular outflows, previously found by
Yun \& Clemens, are roughly perpendicular to the lines connecting the binaries.
A millimeter continuum emission survey revealed that, at
1.3 mm, the sources are the two brightest low-mass young stellar objects
discovered in Bok globules.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by The Astronomical Journal } \
A copy of this paper is available via the World Wide Web. Connect to
http://delphi.cc.fc.ul.pt/papers/binary
\newpage
%% Between these brackets you write the title of your paper:
{\large\bf{A Search For Radio Continuum Emission From Young Stellar Objects in Bok Globules }}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{ Jo\~{a}o Lin Yun$^1$, Miguel C. Moreira$^1$, Jos\'e M. Torrelles$^2$,
Jos\'e M. Afonso$^1$, \& Nuno C. Santos$^1$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1${Departamento de F\'{\i}sica, Universidade de Lisboa, Campo Grande,
Ed. C1, 1700 Lisboa, Portugal} \\
$^2${Instituto de Astrof\'{\i}sica de Andaluc\'{\i}a (CSIC), C/ Sancho Panza
S/N, Ap. Correos 3004, 18080 Granada, Spain}
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: yun@delphi.cc.fc.ul.pt}
%% Within the following brackets you place your text:
{
We present results of a VLA-D search of 3.6 cm continuum emission toward a
selected sample of Bok globules carried out to better characterize their
stellar contents. A total of forty-one radio sources were detected.
Eleven of these sources are located within the optical extents of the globules
and may correspond to embedded sources.
We identify seven candidates to protostars of Class~0. We also identify
five globules without any sign of star formation in infrared or centimeter
wavelengths. These starless globules are candidates to being ideal laboratories
for studying the physical conditions of pre-collapsing cloud cores.
Virtually all the globules with positive radio continuum detections were also
previously found to have associated molecular outflows. This result supports the scenario in which the radio continuum emission arise from shock-ionized circumstellar gas.
}
% Here you write which journal accepted your paper, for example:
{ Accepted by {\it The Astronomical Journal} }
A copy of this paper is available via the World Wide Web. Connect to
http://delphi.cc.fc.ul.pt/papers/vla
\vspace{0.5cm}
%% Between these brackets you write the title of your paper:
{\large\bf{Infrared coronal-line emission from PMS binaries:
Testing the colliding winds model.}}
%% Here comes the author(s) of the paper, please indicate within $^...$
%% the number which corresponds to the institute of each author.
{\bf{S.A. Zhekov$^{1}$, F. Palla$^2$ \& T. Prusti$^3$}}
%% Here you write your institute name(s) and address(es),
%% the number in $^..$ indicates your author number, for example:
$^1$ {Space Research Institute, Bulgarian Academy of Sciences,
Moskovska Str. 6, Sofia 1000, Bulgaria} \\
$^2$ {Osservatorio Astrofisico di Arcetri, L.go E. Fermi, 5, I-50125 Firenze,
Italy} \\
$^3$ {Astrophysics Division, Space Science Department, ESTEC, Postbus
299, NL--2200 AG Noordwijk, The Netherlands }
%% Here you may write the e-mail address of one or more of the authors
%% who will act as contact person for preprint requests etc., for example:
{E-mail contact: palla@arcetri.astro.it}
%% Within the following brackets you place your text:
{ We present model calculations of infrared-coronal-lines emission that arise
from colliding supersonic winds in pre-main-sequence binary stars. For typical
wind velocities between 300 and 500 km~s$^{-1}$, the interaction region has a
temperature range well suited for coronal lines to attain peak emissivities.
Infrared spectral line observations at wavelengths $>$1$\mu$m~ can provide a
unique opportunity to probe the physical conditions of the gas flows
in these systems. We derive simple scaling laws that allow to estimate the
coronal line fluxes as a function of the model parameters and compare
the results with those obtained for the X-ray emission.
The advantage of using coronal lines instead of X-rays to test
the colliding winds paradigm is the greatly reduced abssorption at
infrared wavelengths. Finally, we discuss the possibility of detecting
the most intense lines from known binary systems. }
% Here you write which journal accepted your paper, for example:
{ Accepted by Monthly Not. Roy. Astron. Soc., pink pages}
\newpage
\begin{center}
{\Large\em Dissertation Abstracts}
\end{center}
\begin{center}
%% Between these brackets you write the title of your thesis:
{\Large\bf{Star Formation in Lynds 1641}}
\vspace*{0.5cm}
%% Here comes your name
{\bf{ Lori E. Allen }}
%% Here you write the institute where your thesis work was conducted, e.g.:
{Thesis work conducted at: Five College Astronomy Dept. University of Massachusetts, Amherst, MA, USA}
%% Here comes your present postal address (if you are about to move and know
%% your coming address give it as well) e.g.:
{Current address: School of Physics, University of New South Wales,
Sydney, NSW 2052, Australia}
%% (if you use this part, remove %%)
%% {Address as of XX XXX 1994: }
%% Here comes your e-mail address:
{Electronic mail: lea@newt.phys.unsw.edu.au}
%% Name of your adviser:
{Ph.D dissertation directed by: Karen M. Strom}
%% Month and Year of thesis:
{Ph.D degree awarded: November 1995}
\vspace*{0.8cm}
\end{center}
%% Within the following brackets you place your text:
{ We conducted an extensive multi-wavelength study of the nearest
giant molecular cloud, L1641, with the goal of characterizing its
stellar populations. At a distance of approximately 500 pc, L1641
provides an excellent opportunity for studying star formation over the
entire range of stellar masses, and the star formation history in a
region thought representative of those dominating stellar production
in the Milky Way.
Our approach combines imaging surveys at optical and infrared
wavelengths with spectroscopic surveys at $\lambda\lambda$
6000-9000\AA\, to measure stellar luminosities and effective
temperatures. Stellar ages and masses are then estimated from
comparison of L$_*$, T$_{eff}$ with pre-main sequence evolutionary
tracks. The stars for which we have obtained classifiable spectra as
well as optical $(R,I)$ and near-infrared and near-infrared $(J,H,K)$
photometry number $\sim$300, and are contained within four regions,
each approximately 20$'$ square (2.5 $\times$ 2.5 pc).
Our 2.25m$\mu$ images reveal both modest aggregates of several tens of
stars and stars distributed at random across the face of the cloud; we
find no evidence of rich (N $\gg$ 100 stars) clusters. The aggregate
members appear to have formed within the past 1 Myr, while the
distributed population contains both young stars (t $